When Olympia Snowe, the Republican senior senator from Maine, announced her plans to retire from Congress last month, the consensus among politicos was that her move would behoove the opposing party- the Democrats.

But the filing deadline to qualify for the ballot in the state's June 12 primary was today at 5 p.m., and the outlook for the Democrats is not so clear.

Maine has been friendly territory for Democrats in recent years. The state has gone Democratic in the past three presidential elections, and both of Maine's House reps are Democrats. The party has a deep bench of strong candidates: Reps. Chellie Pingree and Mike Michaud, and former Gov. John Baldacci were viewed as strong possibilities to claim Snow's sought-after seat. All three, however, have decided against running.

Three Democrats are currently set to run: Matt Dunlap, a former secretary of state for Maine, State Senator Cynthia Dill, and State Rep. John Hinck.

On the Republican side the field is twice the size. Six candidates have thrown their hats into the ring; current Secretary of State Charlie Summers, Attorney General William Schneider, State Treasurer Bruce Poliquin, State Sen. Debra Plowman, former Maine Senate President Rick Bennett and Scott D'Ambroise, a Tea Party candidate who entered the race before Snowe announced her retirement.

The big candidate, though, the one who has so far gained the most attention, doesn't represent either party. The candidate is Angus King, the former independent governor who served the state from 1995-2003. King's background in the public and private sectors appeals to both Republicans and Democrats.

"He's a very successful businessman who has done a great deal of work in investing in green energy, and I think that kind of typifies how he's able to appeal to both Republicans and Democrats," said John Baughman, an associate professor of politics at Bates College in Lewiston.

Early polling suggests King is the clear front-runner in the race, and Baughman explained that King's decision to run was likely the motivating factor for the more well-known Democrats otherwise puzzling lack of presence.

"Democrats have in the back of their minds what happened in 2010," said Baughman, referring to Maine's gubernatorial race that year.

"In 2010, Democratic voters ended up splitting votes between the party nominee, Libby Mitchell, and independent Elliot Cutler, allowing a conservative candidate to win with about 39 percent of the vote. And it was pretty clear that if either Mitchell or Cutler had dropped out of the race that LePage, the Republican (and current Maine governor) would have lost. The Democrats lost a winnable governor's seat in a fairly blue state, and they did not want that to happen again."

King, who has suggested he won't caucus with either party if elected, has supported both Republicans and Democrats in the past. In 2000, he endorsed George W. Bush for president. Recently, King told the Associated Press that he supported Obama's bid for re-election, saying, "This year, seeing the likely alternatives, I think the president should be re-elected."

But it's nearly impossible for senators to remain completely independent once in Congress. If they want to receive good committee assignments, they must at least indicate some preference for one side or the other, and in this regard, King does look like a better bet for Democrats than Republicans.

"In comparison with the way Olympia Snowe had been voting over the last couple of years, he's certainly going to be a more liberal vote than that, but I think he's even going to be voting with the Democrats more often than the earlier, more moderate Olympia Snowe too," Baughman said. "I think he's going to end up caucusing with the Democrats on most issues."

Republicans are trying to highlight this belief that King would likely end up being more Democrat than anything else.

"Several strong Republican candidates have stepped forward in Maine, and we look forward to a healthy and spirited primary," Brian Walsh, spokesman for the National Republican Senatorial Committee, wrote to ABC News. "This stands in contrast to the other side, where national Democrats appear to have anointed 'independent' Angus King in a smoke-filled backroom in Washington. So we look forward to the contrast that the campaign ahead will bring."

The Democratic Senatorial Campaign Committee, the Democratic counterpart to the NRSC, has dismissed this accusation, saying they're planning to stay neutral in the primary.

"The DSCC will remain neutral in the Democratic primary" DSCC spokesman Matt Canter told ABC News. "Now that the filing period has ended, we will be speaking with each of the Democratic candidates along with other Democrats in Maine and make an ongoing assessment about the race."